You say "Custom build version". How custom/ized is the build? Does this happen on stock builds?
Reason I ask is because some custom builds have bugs like you're describing. Especially with having to toggle airplane mode to get a connection.
Since @pc747 showed us how to get ADB on a Mac, I'm going to show how I get this working on Windows.
First you'll need this SDK Platform Tools. This is the actual Platform Tools folder that's in the Android SDK. So you'll only need about 15MB of space as opposed to the 28GB needed for the whole...
@69Rixter If you flash a new system then you should be good. The only issue is, if you haven't enabled any backups for things like contacts, photos, etc then that data may be gone forever
Do you have a computer? Also, can this update be downloaded to a computer?
If both answers are Yes, then...
Have you enabled the Developer option in Settings/System/About phone.. Tap on Build Number to enable USB Debugging? If not then try. If you have already enabled USB Debugging then select 'Revoke USB debugging authorization' and toggle USB Debugging off then on